Peerless Watercolors by Nicholson: These watercolors are great for taking on the go, or even working from your desk. They are extremely high concentrations of watercolors.
This is what it says on their website:
The most convenient form yet devised to keep colors clean and available for instant use. The color sheet is a heavy film of highly concentrated pure color of intense strength and absolute solubility. The color is coated on one side of a special paper fabric that readily discharges when it comes into contact with water or any soluble mixture.
What I've done is cut off approx a 1" x 1/2" piece of each color and mounted them with double sided tape (Sookwang - Be Creative Tape) to a piece of heavy clear plastic from some left over packaging. I attached the clear plastic to a piece of white cardstock which I had printed out the names of the colors and added a sample of the color beneath the name. It's so easy to travel with. Smaller than a sheet of paper (8.5 x 9") and thinner than anything you could transfer regular paints to. I keep it in a plastic page protector as well, for safety, so the colors don't accidently transfer to anything else. I also have one of my small water brushes handy.
A color chip this size lasts for ages and is really easy to replace with a new piece from the main sheet in the package.